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Bird Flight

Bird flight

Flight is the mode of locomotion used by most of the world’s bird species. It is important to birds for feeding, breeding and avoiding predators.

Evolution and purpose of bird flight

The origin of bird flight is still somewhat unclear, even though most paleontologists agree that birds evolved from small theropod dinosaurs. It seems likely that they evolved from ground living species, with flight developing after the evolution of feathers. It seems likely in this case that flight evolved as a result of benefits in the pursuit of small airborne prey items (such as insects), possibly subsequently becoming useful as a predator avoiding behavior. Flight is more energetically expensive in larger birds, and many of the largest species fly by soaring (gliding without flapping their wings) most of the time. Many physiological adaptations have evolved that make flight more efficient. Today birds use flight for many purposes. It is still used by some species to obtain prey on the wing, as well as foraging, to commute to feeding grounds, and migrate between the seasons. Flight's importance in avoiding predators can be shown in the frequency with which it is lost when birds reach isolated oceanic islands that lack ground-based predators. It is also used by some species to display during the breeding season and to reach safe isolated places for nesting.

Basic mechanics of bird flight

oceanic island The fundamentals of bird flight are similar to those of aircraft. Lift force is produced by the action of air-flow on the wing, which is an airfoil/aerofoil. The lift-force is because the air has a lower air pressure just above the wing and higher pressure below. When gliding, both birds and gliders obtain both a vertical and a forward force from their wings. This is possible because the lift force is generated at right angles to the air-flow, which in level flight comes from slightly below the wing. The lift force therefore has a forward component. (Weight always acts vertically downwards and so cannot provide a forward force. Without a forward component a gliding bird would merely descend vertically.) gliders When a bird flaps, as opposed to gliding, its wings continue to develop lift as before but they also create an additional forward and upward force, thrust, to counteract its weight and drag. Flapping involves two stages, the down-stroke, which provides the majority of the thrust, and the up-stroke, which can also (depending on the bird’s wings) provide some upward force. At each up-stroke the wing is slightly folded inwards to reduce upward resistance. Birds change the angle of attack between the up-strokes and the down-strokes of their wings. During the down-stroke the angle of attack is increased and is decreased during the up-stroke. There are three types of drag that impede a bird's progress: frictional drag (caused by the friction of air and body surfaces), form drag (due to frontal area of the bird) and lift-induced drag (caused by the wingtip vortices).

The wing

The bird's forelimbs, the wings, are the key to bird flight. Each wing has a central vane to hit the wind, composed of three limb bones, the humerus, ulna and radius. The hand, or manus, which ancestrally was composed of five digits, is reduced to three digits (digit II, III and IV), the purpose of which is to serve as an anchor for the primaries (or metacarpo-digitals), one of two groups of feathers responsible for the airfoil shape. The other set of flight feathers that are behind the carpal joint on the ulna, are called the secondaries or cubitals. The remaining feathers on the wing are known a coverts, of which there are three sets. The wing sometimes has vestigial claws, in most species these are lost by the time the bird is adult (such as the Hoatzin), but claws are retained into adulthood by the Secretary Bird, the screamers and finfoots.

Wing shape and flight

The shape of the wing is important in determining the type of flight of which the bird is capable, planform. This restricts the bird in some ways and enhances the bird in others. Wing shape can be described in terms of two parameters, aspect ratio and wing loading. Aspect ratio is the ratio of wing breadth to the mean of its Chord, or mean wingspan divided by wing area. Wing loading is the ratio of weight to wing area. Amongst the birds there are four main kinds of wing that the majority of birds use, although in some cases wings may fall between two of the categories. These types of wings are elliptical wings, high speed wings, high aspect ratio wings and soaring wings with slots.

Elliptical wings

Elliptical wings are short and rounded, having a low aspect ratio, allowing for tight maneuvering in confined spaces such as might be found in dense vegetation. As such they are common in forest raptors (such as Accipiter hawks), and many passerines, particularly non-migratory ones (migratory species have longer wings). They are also common in species that use a rapid take off for defense, such as pheasants and partridges.

High speed wings

High speed wings are short, pointed wings that combined with a heavy wing loading and rapid wingbeats provide an energetically expensive high speed. This type of flight is used by the bird with the fastest wing speed, the Peregrine Falcon, as well as by most of the ducks. The same wing shape is used by the auks for a different purpose; auks use their wings to "fly" underwater.

High aspect ratio wings

auk High aspect ratio wings, which usually have low wing loading and are far longer than they are wide, are used for slower flight, almost hovering (as used by kestrels, terns and nightjars) or alternatively by birds that specialize in soaring and gliding flight, particularly that used by seabirds, dynamic soaring, which use different wind speeds at different heights(wind shear) above the waves in the ocean to provide thrust.

Soaring wings with deep slots

These are the wings favored by the larger species of inland birds, such as eagles, vultures, pelicans, and storks. The slots at the end of the wings, between the primaries, reduce the turbulence at the tips, whilst the shorter size of the wings aids in takeoff (High aspect ratio wings require a long taxi in order to get airborne).

Hovering

Hovering is a demanding but useful ability used by several species of birds (and specialized in by one family). Hovering, literally generating lift through flapping alone rather than as a product of thrust, demands a lot of energy. This means that it is confined to smaller birds; the largest bird able to truly hover is the Pied Kingfisher, although larger birds can hover for small periods of time. Larger birds that hover do so by flying into a headwind, allowing them to utilize thrust to fly slowly but remain stationary to the ground (or water). Kestrels, terns and even hawks use this windhovering. Pied Kingfisher Most birds that hover have high aspect ratio wings that are suited to low speed flying. One major exception to this are the hummingbirds, which are among the most accomplished hoverers of all the birds. Hummingbird flight is different to other bird flight in that the wing is extended throughout the whole stroke, the stroke being a symmetrical figure of eight, with the wing being an airfoil in both the up- and down-stroke. Some hummingbirds can beat their wings 52 times a second, others do so less frequently.

Take-off and landing

Take-off can be one of the most energetically demanding aspects of flight, as the bird needs to generate enough airflow under the wing to create lift. In small birds a jump up will suffice, while for larger birds this is simply not possible. In this situation, birds need to take a run up in order to generate the airflow to take off. Large birds often simplify take off by facing into the wind, and, if they can, perching on a branch or cliff so that all they need to do is drop off into the air. Landing is also a problem for many large birds with high airspeeds. This problem is dealt with in some species by aiming for a point below the intended landing area (such as a nest on a cliff) then pulling up beforehand. If timed correctly then the airspeed once the target is reached is virtually nil. Landing on water is simpler, and some species, such as swans, are only able to land on water.

Adaptations for flight

The most obvious adaptation to flight is the wing, but because flight is so energetically demanding birds have evolved several other adaptations to improve efficiency when flying. The bird skeleton is hollow to reduce weight, and many unnecessary bones have been lost (such as the bony tail of the early bird Archaeopteryx), along with the toothed jaw of early birds, which has been replaced with a lightweight beak. The vanes of the feathers have hooklets called barbules that zip them together, giving the feathers the strength needed to hold the airfoil (these are often lost in flightless birds). The large amounts of energy required for flight have led to the evolution of a mono directional pulmonary system, that provides the large quantities of oxygen required for the high respiration rate. This high metabolic rate produces large qualities of radicals in the cells, these damage the DNA and can lead to tumours. However, birds do not suffer from the expected shorted life span as their cells have evolved a more efficient antioxidant system than those of other groups of animals.

References

- Del Hoyo, Josep, et al. Handbook of Birds of the World Vol 1. 1992. Barcelona: Lynx Edicions, ISBN 8487334105.
- Brooke, Michael and Tim Birkhead (editors). The Cambridge Encyclopedia of Ornithology. 1991. Cambridge: Cambridge University Press. ISBN 0521362059.
- Campbell, Bruce, and Elizabeth Lack (editors). A Dictionary of Birds. 1985. Calton: T&A D Poyse. ISBN 0856610399.
- Wilson, Barry (editor). Readings from Scientific American, Birds. 1980. San Francisco: WH Freeman. ISBN 0716712067.
- Alexander, David E. Nature's Flyers: Birds, Insects, and the Biomechanics of Flight. 2002(hardcover) and 2004(paperback). Baltimore: The Johns Hopkins University Press. ISBN 0801867568(hardcover) and 0801880599(paperback). Category:Ornithology Category:Birds Category:Aerodynamics

Animal locomotion

In biology and physics, animal locomotion is the study of how animals move, and is part of biophysics. Much of the study is an application of Newton's third law of motion: if at rest, to move forwards an animal must push something backwards. Terrestrial animals must push the solid ground, swimming and flying animals must push against a fluid (either air or water). The topic splits into five disjoint categories: # animal locomotion on land (walking and running) # animal locomotion in air (bird flight) # animal locomotion in water (swimming including fish and ducks) # animal locomotion on the surface layer (small animals relying on surface tension such as the water strider) # animal locomotion by water-walkers (the Common Basilisk). The distinction between the second and third topics is that in the second, the animal does not need to expend energy to defeat gravity; in or on the water, buoyancy counteracts the animal's weight. Category:Locomotion

Paleontology

Paleontology (the American spelling; the British spelling is palaeontology) is the study of the developing history of life on earth, of ancient plants and animals based on the fossil record, evidence of their existence preserved in rocks. This includes the study of body fossils, tracks, burrows, cast off parts, fossilized feces ("coprolites"), and chemical residues.

Overview

Modern paleontology sets ancient life in its contexts, by studying how long-term physical changes of global geography ("paleogeography") and climate ("paleoclimate") have affected the evolution of life, how ecosystems have responded to these changes and have changed the planetary environment in turn, and how these mutual responses have affected today's patterns of biodiversity. So paleontology overlaps with geology, the study of rocks and rock formations, and with botany, biology, zoology, and ecology, fields concerned with living creatures and how they interact. Palynology is the study of pollen, whether modern or geological. The major subdivisions of paleontology include paleozoology (animals), paleobotany (plants), and micropaleontology (microfossils). Paleozoologists may specialize in invertebrate paleontology, which deals with animals without backbones, or in vertebrate paleontology, dealing with fossils of animals with backbones, including fossil hominids (paleoanthropology). Micropaleontologists study microscopic fossils, including organic-walled microfossils whose study is called palynology. There are many developing specialties such as paleoecology, paleobotany, ichnology (the study of tracks and burrows) and taphonomy, the study of what happens to organisms after they expire. Major areas of study include the correlation of rock strata with their geologic ages and the study of evolution of lifeforms. Paleontology utilizes the same classic binomial nomenclature scheme devised for the biology of living things by the mid 18th century Swedish biologist Carolus Linnaeus and increasingly sets these species in a genealogical framework, showing their degrees of interrelatedness using the still somewhat controversial technique of "cladistics". The primary economic importance of paleontology lies in the use of fossils to determine the age and nature of the rocks that contain them or the layers above or below. This information is vital to the mining industries and especially the petroleum industry. Simply looking at the fossils contained in a rock remains one of the fastest and most accurate means of telling how old that rock is. Fossils were known by primitive man and were sometimes identified correctly as the remains of ancient lifeforms. The organized study of paleontology dates from the late 18th century.

Notable paleontologists

Paleontologists are among the more colorful and eccentric figures in the history of science. Important figures include the Englishman William Smith who first noted that similar fossil sequences were found regionally and Georges Cuvier who initiated the study of ancient animals based on living animals. Notable American figures include Edward Drinker Cope, Othniel Charles Marsh, Paul Sereno, Henry Fairfield Osborn, Louis Agassiz, Charles Walcott, and Roy Chapman Andrews. Notable European paleontologists include the Swedish-speaking Finn Björn Kurtén, Czech paleoentomologist Jarmila Kukalova-Peck. Franz Nopcsa von Felsö-Szilvás is often credited for being the founder of palaeobiology, a field of inquiry dealing with the biological and ecological functions that can be deduced from fossils. History includes a number of prominent paleontologists. Charles Darwin collected fossils of South American mammals during his trip on the Beagle and examined petrified forests in Patagonia. Thomas Jefferson took a keen interest in mammoth bones. Besides looking at mammal teeth and digging up penguins, George Gaylord Simpson played a crucial role in bringing together ideas from biology, paleontology, and genetics to help create the "Modern Synthesis" of evolutionary biology; his book "Tempo and Mode" is a classic in the field. Prominent names in invertebrate paleontology include Steven Stanley, Stephen Jay Gould, David Raup, Geerat Vermeij, and Jack Sepkoski who have done much to expand our understanding of long-term patterns in the evolution of life on earth. The same is the case with Croatian scientist Dragutin Gorjanovic-Kramberger and his discovery of the "Krapina Man". Other paleontologists include Yves Coppens. More modern figures in paleontology include John Ostrom, Bob Bakker, David B. Weishampel and Jack Horner.

Research

The work done in paleontology can be divided into field work, fossil preparation and laboratory processing, identification of taxa and other data collection, systematic description of new species, and collections management.

External links

- [http://www.dinosaurnews.org Dinosaurnews] the free dinosaur zine (very popular site, with the latest international news about dinosaurs).
- [http://www.ub.es/dpep/meganeura/meganeura.htm Meganeura] Website about insect evolution and fossil record.
- [http://www.nmnh.si.edu/paleo/geotime/ Smithsonian's Paleobiology website: a good introduction]
- [http://www.ucmp.berkeley.edu/FAQ/faq.html University of California Museum of Paleontology FAQ About Paleontology]
- [http://www.krapina.com/neandertals/index_en.htm Krapina Man] Category:Earth sciences Category:Geology
- paleontology ko:고생물학 ja:古生物学 ]

Dinosaur

Dinosaurs are vertebrates that dominated the terrestrial ecosystem for over 160 million years. Non-avian dinosaurs became extinct at the end of the Cretaceous period, 65 million years ago. Knowledge about dinosaurs comes from both fossil and non-fossil records, including fossilized bones, feces, trackways, gastroliths, feathers, impressions of skin, internal organs and soft tissues. Since the first dinosaur was recognized in the 19th century, their mounted, fossilized skeletons have become major attractions at museums around the world. Dinosaurs have become a part of world culture and remain consistently popular, especially among children. They have been featured in best-selling books and blockbuster films such as Jurassic Park, and new discoveries are regularly covered by the media. The term is also used informally to describe any prehistoric reptile, such as the pelycosaur Dimetrodon, the winged pterosaurs, and the aquatic ichthyosaurs, plesiosaurs, and mosasaurs, though none of these are dinosaurs. The on-going dinosaur renaissance began in the 1970s and was triggered, in part, by John Ostrom's discovery of Deinonychus, an active, vicious predator that may have been warm-blooded (homoeothermic), in marked contrast to the prevailing image of dinosaurs as sluggish and cold-blooded. Vertebrate paleontology has also become a global science, with major new discoveries in previously unexploited regions, including South America, Madagascar, Antarctica, and most significantly the amazingly well-preserved feathered dinosaurs in China, which have further solidified the link between dinosaurs and their living descendants, modern birds. The widespread application of cladistics, which rigorously analyzes the relationships between biological organisms, has also proved tremendously useful in classifying dinosaurs, which are still known from an incomplete fossil record.

What is a dinosaur?

Definition

fossil record at the Smithsonian National Museum of Natural History.]] The superorder or clade "Dinosauria" was formally named by the English scientist Richard Owen in 1842. The term is a combination of the Greek words deinos ("terrible" or "fearfully great" or "formidable") and sauros ("lizard" or "reptile"). Contrary to popular perception, the name was chosen to express Owen's awe at the size and majesty of the extinct animals, not out of fear or trepidation at their size and formidable arsenal. Dinosaurs are extremely varied. Some were herbivorous, others carnivorous. Some dinosaurs were bipedal, others quadrupedal, while others could walk easily on both two and four legs, such as the dinosaur Ammosaurus. Under phylogenetic taxonomy, Dinosaurs are defined as all descendants of the most recent common ancestor of Triceratops and modern birds. Ornithischia is defined as all taxa sharing a more recent common ancestor with Triceratops than with Saurischia. Saurischia is defined as all taxa sharing a more recent common ancestor with birds than with Ornithischia. It has also been suggested that Dinosauria be defined as as all the descendants of the most recent common ancestor of Megalosaurus and Iguanodon There is an almost universal consensus among paleontologists that birds are the descendants of theropod dinosaurs. Using the strict cladistical definition that all descendants of a single common ancestor are related, modern birds are dinosaurs and dinosaurs are, therefore, not extinct. Modern birds are classified by most paleontologists as belonging to the subgroup Maniraptora, which are coelurosaurs, which are theropods, which are saurischians, which are dinosaurs. However, birds are morphologically distinct from their reptilian ancestors, and referring to birds as "avian dinosaurs" and to all other dinosaurs as "non-avian dinosaurs" is clumsy. Birds are still birds, at least in popular usage and among ornithologists. It is also technically correct under the older Linnaean classification system, which accepts taxa that exclude some descendants of a single common ancestor (paraphyletic taxa). Paleontologists mostly use cladistics in their classifications, which classifies birds as dinosaurs, but many other scientists do not. As a result, this article will use "dinosaur" as a synonym for "non-avian dinosaur", and "bird" as a synonym for "avian dinosaur".

Size

Only a tiny percentage of animals ever fossilize, and most of these remain buried in the earth. As a result, the smallest and largest dinosaurs will probably never be discovered. Even among those specimens that are recovered, few are known from complete skeletons, and impressions of skin and soft tissue are rare. Reconstructing a skeleton by comparing the size and morphology of bones to those of similar, better-known species is inexact, and restoring the muscles and other organs is, at best, educated guesswork. smallest and largest dinosaurs.]] smallest and largest dinosaurs While the largest and smallest dinosaurs will probably remain unknown, and a comparison between existing specimens is imprecise, it is clear that, as a group, dinosaurs were large. By dinosaur standards the sauropods were gigantic. The smallest sauropods were larger than anything else in their habitat, and the largest were an order of magnitude more massive than anything else that has ever walked the Earth. The tallest and heaviest dinosaur known from a complete skeleton is the Brachiosaurus, which was discovered in Tanzania between 1907–12. It is now mounted in the Humboldt Museum of Berlin and is 12 m (38 ft) tall and probably weighed between 30,000–60,000 kg (30–70 short tons). The longest dinosaur is the 27 m (89 ft) long Diplodocus, which was discovered in Wyoming and mounted in Pittsburgh's Carnegie Natural History Museum in 1907. There were larger dinosaurs, but they are only known from a scant number of fossil samples. The largest specimens on record all date from the 1970s or later, and include the massive Argentinosaurus, which may have weighed 80,000–100,000 kg (90–110 tons); the longest, the 40 m (130 ft) long Supersaurus; and the tallest, the 18 m (60 ft) Sauroposeidon, which could have reached a sixth-floor window. Dinosaurs were the largest of all terrestrial animals. The largest elephant on record weighed 12,000 kg (13.5 tons), and the tallest giraffe was 6 m (20 ft) tall. Even the giant prehistoric mammals such as the Indricotherium and the Columbian mammoth were dwarfed by the giant sauropods. Only a small handful of aquatic animals approach it in size, of which the blue whale is largest, reaching up to 190,000 kg (210 tons) and 33.5 m (110 ft) in length. Not including modern birds like the bee hummingbird, the smallest dinosaurs known were about the size of a crow or a chicken. The Microraptor, Parvicursor, and Saltopus were all under 60 cm (2 ft) in length. In fact, most dinosaurs were much smaller than we would expect, with the average size of a dinosaur being around the size of a large sheep.

Behavior

Interpretations of behavior based on the pose of a body fossil and its habitat, computer simulations of their biomechanics, and comparison with modern animals in similar ecological niches rely on speculation and promise to generate controversy for the foreseeable future. However, it is likely that at least the behaviors common in both of their closest living relatives, crocodiles and birds, are also common among dinosaurs. It should be of note that nearly all interpretations of evidence are subject to change, as theories surrounding dinosaurs evolve continuously. The first evidence of herding behavior was the 1878 discovery of 31 Iguanodon that perished together in Bernissart, Belgium, after they fell down a deep ravine, drowning as the latter was filled with rainwater. Similar mass deaths and trackways suggest that herd or pack behavior was common among many dinosaur groups. Trackways of hundreds or even thousands of herbivores indicate that duck-bills (hadrosaurids) may have moved in great herds, like the American Bison or the African Springbok. Sauropod tracks document that they traveled in groups composed of several different species, at least in Oxford, England, and others kept their young in the middle of the herd for defense according to trackways at Davenport Ranch, Texas. Dinosaurs may have congregated in herds for defense, migration, or to care for their young. migration Jack Horner's 1978 discovery of a Maiasaura ("good mother dinosaur") nesting ground in Montana demonstrated parental care long after birth among the ornithopods, and similar nesting behavior and even huge nesting colonies like those of penguins have been discovered of other Cretaceous dinosaurs like the Patagonian sauropod Saltasaurus (in 1997). The Mongolian maniraptoran Oviraptor was even discovered in a chicken-like brooding position in 1993, which may mean it was covered with an insulating layer of feathers that kept the eggs warm. Trackways have also confirmed parental behavior among sauropods and ornithopods from the Isle of Skye in the United Kingdom. Nests and eggs are known from most major groups of dinosaurs, and it appears likely that dinosaurs communicated with their young, like modern birds and crocodiles. The crests and frills of some dinosaurs, like the marginocephalians, theropods and lambeosaurines, may have been too fragile for active defense, so they were probably used for sexual or aggressive displays, though little is known about dinosaur mating and territorialism. Communication is also an enigma, but the hollow crests of the lambeosaurines may have been resonance chambers used for a wide range of vocalizations. One of the most valuable fossils, a Velociraptor attacking a Protoceratops, was discovered in the Gobi Desert in 1971, proving that dinosaurs did indeed attack and eat each other. While cannibalistic behavior among theropods is no surprise, it was confirmed by tooth marks from Madagascar in 2003. Compared to the later mammalian radiation in the Cenozoic, there seem to be no burrowing and few climbing dinosaurs. Biomechanics has given insight into how fast dinosaurs could run, whether diplodocids could create sonic booms by snapping their tails like a whip, whether giant theropods had to slow down when rushing for food to avoid fatal injuries, and if sauropods could float.

Study of dinosaurs

Fields of study

Information on dinosaurs is obtained from a variety of fields of study including Physics, Chemistry, Biology, and the Earth Sciences (which includes Paleontology). Activities include the discovery, reconstruction and conservation of dinosaur fossils and the interpretation of those fossils to better understand the evolution, classification and behavior of dinosaurs.

Classification

Main article: Dinosaur classification Dinosaurs (including birds) are archosaurs, like modern crocodilians. These are set apart by having diapsid skulls, having two holes where jaw muscles attach, called temporal fenestrae. Most reptiles (including birds) are diapsids; mammals, with only one temporal fenestra, are called synapsids; and turtles, with no temporal fenestra, are anapsids. Dinosaurs also have teeth that grow from sockets (an archosaur characteristic) rather than as direct extensions of the jaw bones, as well as various other characteristics. Within this group, the dinosaurs are set apart most noticeably by their gait. Instead of legs that sprawl out to the side, as found in lizards and crocodylians, they have legs held directly under their body. All dinosaurs were land animals. Many other types of reptiles lived at the same time as the dinosaurs. Some of these are commonly, but incorrectly, thought of as dinosaurs: these include plesiosaurs (which are not closely related to the dinosaurs) and pterosaurs, which developed separately from reptilian ancestors in the late Triassic. Dinosaurs are divided into two major orders, the Saurischia and the Ornithischia, on the basis of hip structure. Saurischians (from the Greek meaning "lizard hip") are dinosaurs that retained the hip structure of their ancestors. They include all the theropods (bipedal carnivores) and sauropods (long-necked herbivores). Ornithischians (from the Greek meaning "bird-hip") is the other dinosaurian order, most of which were quadrupedal herbivores.

Evolution

Dinosaurs split off from their archosaur ancestors during the Triassic period. The first known dinosaurs appeared approximately 230 Mya, about 20 million years after the Permian-Triassic extinction event wiped out about 70 percent of all biological diversity on the planet. A few lines of primitive dinosaurs diversified rapidly after the Triassic, and quickly expanded until they filled most of the vacant ecological niches. During the reign of the dinosaurs, which encompassed the ensuing Jurassic and Cretaceous periods, nearly every terrestrial animal larger than 1 m in length (that we know of) was a dinosaur. The Cretaceous-Tertiary extinction event, 65 Mya at the end of the Cretaceous, caused the extinction of all dinosaurs except for the line that had already led to the first birds.

Areas of debate

Warm-blooded?

Cretaceous-Tertiary extinction event Scientists have waged a constant and vigorous debate over the temperature regulation of dinosaur blood; at first over its possibility, then over its method, a debate first popularized by Robert T. Bakker, also known as Bob Bakker. From the first discovery of dinosaurs, paleontologists posited that they were ectothermic creatures: "terrible lizards" as their name suggested. This axiomatic expectation implied that dinosaurs were mostly slow, sluggish organisms, comparable to modern reptiles, which need the sun to heat their bodies. However, new evidence of dinosaurs in chilly temperate climates, of polar dinosaurs in Australia and Antarctica where they experienced a six-month chilly and dark winter, of feathered dinosaurs whose feathers provided regulatory insulation, and analysis of blood-vessel structures that are typical of endotherms within dinosaur bone, confirmed the possibility that some dinosaurs regulated their body temperature by internal biological methods, some aided partly by their very bulk. Skeletal structures suggest active lifestyles for theropods and other creatures, behavior more suitable for an endothermic cardiovascular system. Sauropods exhibit fewer endothermic characters. Perhaps some dinosaurs were endothermic and others not. Scientific debate over the details continues, although many paleontologists would now agree that endothermic systems are more likely (Parsons et al., 2001). Complicating this debate, warm-bloodedness can emerge from more than one mechanism. Most discussions of dinosaur endothermia compare them to average birds or mammals, which expend energy to elevate body temperature above that of the environment. Small birds and mammals also possess insulation of some sort, such as fat, fur, or feathers, to slow down heat loss. However, large mammals, such as elephants, face a different problem due to their relatively small surface area to volume ratio (Haldane's principle). This ratio compares the volume of an animal with the area of its skin: as an animal gets bigger, its surface area increases more slowly than its volume. At a certain point, the amount of heat radiated away through the skin drops below the amount of heat produced inside the body, forcing animals to use additional methods to avoid overheating. In the case of elephants, they lack fur, and have large ears which increase their surface area, and have behavioral adaptations as well, such as using the trunk to spray water on themselves and mud wallowing. These behaviors increase cooling through evaporation. Large dinosaurs would presumably have faced the same situation: their size would dictate that they lost heat relatively slowly to the surrounding air, and so could have been what are called bulk endotherms, animals that are warmer than their environments through sheer size rather than any special adaptations like those of birds and mammals. However, so far this theory fails to explain the vast multitudes of dog- and goat-sized dinosaurs, which made up the bulk of the ecosystem in the mesozoic.

Feathered dinosaurs and the bird connection

A number of similiarities occur between birds and non-avian dinosaurs, in fact over a hundred distinct anatomical features are shared by avian dinosaurs and theropod dinosaurs. Feathers bulk endotherms.]] The first good specimen of a "feathered dinosaur" was the 1861 discovery of the Archaeopteryx in Germany, in the Solnhofen limestone, which is a lagerstätte; one of the rare and remarkable geological formations known for their superbly detailed fossils. Coming just two years after Darwin's seminal The Origin of Species, the evidence of a transitional fossil between reptiles and birds spurred the debates between evolutionary biology and creationism. This early bird is so dinosaur-like that, without a clear impression of feathers in the surrounding rock, the specimens are commonly mistaken for Compsognathus. Since the 1990s, a number of feathered dinosaurs have been found, providing clear evidence of the close relationship between dinosaurs and birds. Most of these specimens were local to Liaoning province in northeastern China, which was part of an island continent in the Cretaceous. However, the feathers were only preserved by the lagerstätte of the Yixian Formation; it is therefore possible that dinosaurs elsewhere in the world may have been feathered too, even though the feathers have not been preserved. The feathered dinosaurs discovered so far include Beipiaosaurus, Caudipteryx, Dilong, Microraptor, Protarchaeopteryx, Shuvuuia, Sinornithosaurus, and Sinosauropteryx, and potentially Adasaurus; and dinosaur-like birds like Confuciusornis; all of which come from the same area and formation in northern China. The dromaeosauridae family in particular seems to have been heavily feathered, and at least one dromaeosaurid, Cryptovolans, may have been capable of flight. Skeleton Because feathers are often associated with birds, feathered dinosaurs are often touted as the missing link between birds and dinosaurs. However, the association of multiple skeletal features also shared by the two groups is the more important link for paleontologists. Furthermore, it is increasingly clear that the relationship between birds, dinosaurs and the evolution of flight is more complex than has been previously realized. For example, while it was once believed that birds evolved from dinosaurs in one linear progression, some scientists, most notably Gregory S. Paul, conclude that some dinosaurs, such as the dromaeosaurs, may have evolved from birds, losing the power of flight while keeping their feathers in a manner similar to the ostrich and other ratites. Comparisons of bird and dinosaur skeletons, as well as cladistic analysis, strengthens the case for the link, particularly for a branch of theropods called maniraptors. Skeletal similarities include: the neck, pubis, wrists (semi-lunate carpal), arm and pectoral girdle, shoulder blade, clavicle and breast bone. Reproduction biology breast bone.]] A discovery in a Tyrannosaurus rex skeleton provided more evidence that dinosaurs and birds evolved from a common ancestor and for the first time allowed paleontologists to sex a dinosaur. When laying eggs, female birds have a special type of bone, called a medullary bone, that grows in their limbs, forming a layer inside the hard outer bone. It is rich in calcium and used for making eggshells. The presence of endosteally derived bone tissues lining the interior marrow cavities of portions of the Tyrannosaurus rex specimen's hind limb elements suggested similar reproductive strategies, and revealed the specimen to be female (Schweitzer et al., 2005). A dinosaur embryo was found without teeth, which suggests some parental care was required to feed the young dinosaur, possibly the adult dinosaur regurgitated nutrition into the young dinosaur's mouth. This behavior is seen in numerous modern-day bird species; the parent birds regurgitated food into the hatchling's mouth. Lungs Big meat-eating dinosaurs had a complex system of air sacs similar to the setup in today's birds, according to an investigation led by Patrick O'Connor of Ohio University. The lungs of theropod dinosaurs, carnivores that walked on two legs and had birdlike feet, likely pumped air into hollow sacs in their skeletons, as is the case in birds. "What was once formally considered unique to birds was present in some form in the ancestors of birds", O'Connor said. The study was funded in part by the National Science Foundation. Heart and sleeping posture Modern computerized tomography (CT) scans of dinosaur chest cavities, conducted in 2000, found the apparent remnants of complex four-chambered hearts, much like those of today's mammals and birds. A recently discovered troodont fossil demonstrates that the dinosaurs slept like certain birds today, with their heads tucked under their arms. This would allow the head to be kept warm as is shown by modern birds. Gizzard Another piece of evidence that birds and dinosaurs are closely connected is that both birds and dinosaurs have used gizzard stones. The stones are swallowed by the animal to aid digestion and break down hard fibres and food once it enters the stomach. When found in association with fossils, they are called gastroliths. Paleontologists use the stones found in the dinosaur's stomach to determine migration routes, for example, the stone could have been swallowed at a certain point before being carried to another point during migration.

Evidence for Cenozoic dinosaurs

It has been claimed that fossils from El Ojo, South America, represent remains of dinosaurs surviving the extinction and still thriving in the Paleocene epoch. There are also other sporadic claims of post-Cretaceous dinosaur fossils (even a very doubtful finding of dinosaur eggs as late as Eocene). While it is certainly not improbable that some scattered population of some (presumably small) dinosaur species could have survived at least some hundreds of years after the mass extinction, evidence now points to El Ojo (and most other) findings as Cretaceous fossils contaminating Paleocene strata. Nevertheless, it is still theorized that some dinosaur population could have survived the main extinction event isolated in Antarctica, and then being killed by the climatic change.

Bringing dinosaurs back to life

Antarctica.]] There has been much speculation about the availability of technology to bring dinosaurs back to life. The idea proposed in Michael Crichton's book Jurassic Park, using blood from fossilized mosquitos that have been suspended in tree sap since the Mesozoic and then filling in the gaps with frog genes to create the DNA of a dinosaur, is probably impossible. A problem with this theory is that DNA decays over time by exposure to air, water and radiation, thus depleting the chances of salvaging any useful DNA. Decay can be measured by a racemization test. There have been two claims about the successful extraction of ancient DNA from dinosaur fossils, but upon further inspection, neither of these reports could be confirmed (Wang et al., 1997). However, a working visual peptide of a (theoretical) dinosaur has been inferred using analytical phylogenetic reconstruction methods on gene sequences of still-living related species (reptiles and birds) (Chang et al., 2002).

Discovery of probable soft tissue from dinosaur fossils

In the March 2005 issue of Science, (Schweitzer et al.) announced material, after rehydrating, that resembled soft tissue was discovered inside a Tyrannosaurus rex leg bone from the Hell Creek Formation in Montana, from about 68 million years ago. When the fossilized bone was treated over several weeks to remove mineral content (demineralize) from the fossilized bone marrow cavity, Schweitzer found evidence of intact structures such as blood vessels, bone matrix, and connective tissue (bone fibers). Scrutiny under microscope further revealed the putative dinosaur soft tissue had retained fine structures (microstructures) even at the cellular level. It has not been made clear of what this flexible material is actually composed, although many news reports immediately linked it with the movie "Jurassic Park", and the interpretation of the artifact as well as the relative importance of Dr. Schweitzer's discovery is still undecided.

Extinction theories

The extinction of the non-avian dinosaurs is one of the most intriguing problems in paleontology. Only since the 1970s has the nature of this extinction become researched in detail, showing some possible causes of the dinosaur extinction.

Asteroid collision

paleontology, the impact of which may have caused the Dinosaur extinction.]] The theory first proposed by Walter Alvarez in the late 1970s, linked the extinction event at the end of the Cretaceous period to a bolide impact about 65.5 million years ago, based on a sudden change in Iridium levels in fossilized layers. The bulk of the evidence now indicates that a 10 km wide bolide hit the Yucatán Peninsula 65 million years ago, creating the 170 km wide Chicxulub Crater and causing the extinction. Scientists are still disputing whether dinosaurs were in steady decline or still thriving before the meteor struck. Some scientists state that the meteor would have caused an unnatural winter, while others claim that it would have created an unusual heat wave. Although the speed of extinction cannot be deduced from the fossil record alone, the latest models suggest the extinction was extremely rapid. It appears to have been caused by heat from the meteorite impact and the matter ejected from the crater reentering the Earth's atmosphere around the world.

The Oort cloud

Similar to Alvarez's theory, which involved a single comet, the Oort cloud suggests that a vast shower of comets that were dislodged in an astral phenomenon hit the Earth at the same time, causing world wide extinction. The end result would again be an unnatural winter, ultimately freezing the dinosaurs.

Environment changes

The environment during the late Cretaceous was changing dramatically. Volcanic activity was decreasing. This led to a cooling trend as the levels of carbon dioxide diminished. At the eras peak, sea levels are estimated to have been between 100 metres (330 feet) to 250 metres (820 feet) higher than now with no polar ice caps. The planet's temperature was much more uniform, with only a 25 degrees C difference from the polar regions to the equator and much warmer with the poles 50 degrees C warmer than today. The atmosphere's composition had carbon dioxide levels 12 times higher than today's levels, and oxygen formed 32 to 35 percent of the atmosphere, as compared with 21 percent today. But toward the end of the Cretaceous, these levels started to fluctuate wildly. Some hypothesize that climate change combined with the fall of oxygen levels might have led to many species demise, especially if the dinosaurs had a respiratory system commonly found in today's birds - something that would be difficult for an animal as large as a dinosaur with lower oxygen levels to breathe in. Other groups besides dinosaurs became extinct at the same time, including ammonites (nautilus-like mollusks), mosasaurs, plesiosaurs, pterosaurs, herbivorous turtles and crocodiles, most kinds of birds, and many groups of mammals.

History of discovery

Dinosaur fossils have been known about for millennia, though their true nature was not recognized; the Chinese considered them to be dragon bones, while Europeans believed them to be the remains of giants and other creatures killed by the Great Flood. The first dinosaur species to be identified and named was Iguanodon, discovered in 1822 by the English geologist Gideon Mantell, who recognized similarities between his fossils and the bones of modern iguanas. Two years later, the Rev William Buckland, professor of geology at Oxford University, became the first person to describe a dinosaur in a scientific journal, in this case Megalosaurus bucklandii, found near Oxford. The study of these "great fossil lizards" became of great interest to European and American scientists, and in 1842 the English paleontologist Richard Owen coined the term "dinosaur". He recognized that the remains that had been found so far, Iguanodon, Megalosaurus and Hylaeosaurus, had a number of features in common, so decided to present them as a distinct taxonomic group. With the backing of Prince Albert of Saxe-Coburg-Gotha, husband of Queen Victoria, Owen established the Natural History Museum in South Kensington, London, to display the national collection of dinosaur fossils and other biological and geological exhibits. London London In 1858, the first known American dinosaur was discovered in marl pits of the small town of Haddonfield, New Jersey (although fossils had been found before, their nature had not been identified). The creature was named Hadrosaurus foulkii, after the town and the discoverer, William Parker Foulke. It was an extremely important find: Hadrosaurus was the first nearly complete dinosaur skeleton ever found and it was clearly a bipedal creature. This was a revolutionary discovery, as most scientists had thought that dinosaurs walked on four feet like lizards. Foulke's discoveries sparked a dinosaur mania in the United States, which was exemplified by the fierce rivalry of Edward Drinker Cope and Othniel Charles Marsh, who each competed to outdo the other in finding new dinosaurs in what came to be known as the Bone Wars. The feud was probably started when Marsh criticized Cope for putting the bones of a Elastomosaurus on back to front. This started the jealousy and madness of a fight which ensued for the next 30 years, only ending in 1897 when Cope died after spending his entire fortune in the dinosaur hunt. Marsh won the contest by virtue of being better funded through the US Geological Survey. Unfortunately, many of the valuable dinosaur specimens were destroyed or damaged due to the pair's rough approach; often the diggers used dynamite to unearth bones. All together, they discovered 142 new species of dinosaur, with Marsh unearthing 86 new species, while Cope only discovered 56 species. Cope's collection is now at the American Museum of Natural History in New York, while Marsh's is displayed at the Peabody Museum of Natural History at Yale University. Since then, the search for dinosaurs has been carried to every continent on Earth. This includes Antarctica, where the first dinosaur, a nodosaurid Ankylosaurus, was discovered on Ross Island in 1986, though it was 1994 before an Antarctic dinosaur, the Cryolophosaurus ellioti, was formally named and described in a scientific journal. Current "hotspots" include southern South America (especially Argentina) and China, which has produced many exceptional feathered dinosaur specimens due to the arid climate having preserved the skeleton.

In popular culture

feathered dinosaur Dinosaurs were highly successful life forms for some 150 million years; however, even more than their success, it is their extinction that has become part of human culture. Hence dinosaur is sometimes used as a metaphor for people and things that are perceived as being out of date or no longer in touch with the spirit of the times, and therefore ought to be extinct. An example was the manner in which the punk movement described the "progressive" bands that preceded them as "dinosaur groups". One of the most ground breaking movies of its time, Jurassic Park, brought dinosaurs into the media spotlight, proving that dinosaurs were a good selling point for producers. Jurassic Park led to two sequels, The Lost World: Jurassic Park and Jurassic Park 3, both blockbusters in their own right. Due to the popularity of the movies, and their portrayal of T rex as king of the dinosaurs, dinosaurs have become a permanent fixture in today's world, with the Tyrannosaurus rex being the most popular due to the movies portraying him as king of the dinosaur. The Jurassic Park movies also inspired a couple of console games, such as Jurassic Park the video game. Dinosaurs, because of their sizes and perceived aggressiveness, have both long fascinated and terrified the public mind in fictional as well as non-fictional works. This makes them a favorite of both young and old. fictional.]] Notable examples of fictional works include Arthur Conan Doyle's book The Lost World, the 1933 film King Kong and Godzilla. Thus, the possibility of humans and dinosaurs living together has been a recurring theme in fiction: The Valley of Gwangi (1969) and One Million Years BC (1966) (famously starring Raquel Welch in a fur bikini). Ray Harryhausen brought the dinosaurs to life in both films using model animation. Other classic films where dinosaurs have been in the spotlight are Pterodactyl and Spot from The Munsters. The Munsters The development of Computer-generated imagery further enhanced that fantasy and also allowed the production of documentaries; 1999 BBC series Walking with Dinosaurs is a notable example. Dinosaurs, however are not only depicted as cold-blooded reptiles but also as warm-loving and even with friendly personalities, either to appeal to young children such as the 1970s show Land of the Lost, the 1990s' Dinosaurs and the more recent Barney & Friends. For cartoons The Flintstones showcased a stone age family living with dinosaurs, while comic strips such as Calvin and Hobbes and The Far Side feature dinosaur orientated strips frequently. Due to their consumer appeal, many computer and console games have featured dinosaurs as characters. Crash Bandicoot: Warped, Ape Escape, the Turok series, and even Zoo Tycoon have involved dinosaurs in their story lines.

Notes

#Dal Sasso, C. and Singnore, M. (1998). Exceptional soft-tissue preservation in a theropod dinosaur from Italy. Nature 292:383-387. [http://www.dinosauria.com/jdp/misc/scipionyx.html See commentary on the article] # Schweitzer, M.H., Wittmeyer, J.L. and Horner, J.R. (2005). Soft-Tissue Vessels and Cellular Preservation in Tyrannosaurus rex. Science 307:1952 - 1955. [http://news.bbc.co.uk/2/hi/science/nature/4379577.stm See commentary on the article] #[http://news.nationalgeographic.com/news/2002/05/0529_020529_sauropods.html Sauropod tracks] Sauropod tracks are giving paleontologists new information. # Lessem, D. and Glut, D.F. (1993). The Dinosaur Society's Dinosaur Encyclopedia. Random House Inc. ISBN 0679417702. [http://www.isgs.uiuc.edu/faq/dino-faqs/pdq76.html See commentary on the article] # [http://www.browningmontana.com/dinosaurs.html Juvenile Tyrannosaur] A juvenile Tyrannosaur skeleton was found. # [http://search.eb.com/dinosaurs/dinosaurs/BRa.html Oviraptor nesting] Oviraptor nests or Protoceratops? # [http://news.bbc.co.uk/1/hi/scotland/3255494.stm Dinosaur family tracks] Footprints show maternal instinct after leaving the nest. # [http://www.amnh.org/exhibitions/fightingdinos/ex-fd.html Joined forever in death] The discovery of two fossil dinosaurs entangled together proved many theories. # [http://news.nationalgeographic.com/news/2002/12/1219_021219_dinocannibal.html Cannibalistic Dinosaur] The mystery of a dinosaur cannibal. # [http://www.nsf.gov/od/lpa/news/03/pr0336.htm Madagascar cannibal] A cannibal dinosaur is uncovered in Madagascar. # [http://palaeo.gly.bris.ac.uk/Palaeofiles/Tracks/Report7/Speed.html Gait and Dinosaur speed] Gait and his formula on estimating a dinosaur's speed. # [http://www.shef.ac.uk/~es/DINOC01/dinocal1.html Calculate your own Dinosaur speed] More on Gait and his speed calculations. # [http://news.bbc.co.uk/1/hi/sci/tech/78905.stm Injuries from rushing] Dinosaurs were so eager to eat food, they broke their ribs! # [http://www.nserc.ca/news/features/dinosaurs_e.htm Sauropods that floated] Sauropods were the largest animals to float. # [http://news.nationalgeographic.com/news/2005/12/1201_051201_archaeopteryx_2.html Archaeopteryx related to the Deinonychosaurs?] Archaeopteryx is proven to be closely related to Deinonychosaurs. # O'Connor, P.M. and Claessens, L.P.A.M. (2005). Basic avian pulmonary design and flow-through ventilation in non-avian theropod dinosaurs. Nature 436:253. # [http://www.guardian.co.uk/life/news/story/0,12976,1326559,00.html Bird-like sleeping position for Dinosaur] Even more evidence proving birds are dinosaurs. # [http://www.sciencemag.org/cgi/content/full/sci;307/5717/1952 Cellular preservation inside T rex blood vessels] Can these cells be used to bring the Tyrannosaurus rex back to life? # Koeberl, C. and MacLeod, K.G. (2002). Catastrophic Events and Mass Extinctions. Geological Society of America. ISBN 0813723566.

References

- Kevin Padian, and Philip J. Currie. (1997). Encyclopedia of Dinosaurs. Academic Press. ISBN 0122268105. (Articles are written by experts in the field).
- Paul, Gregory S. (2000). The Scientific American Book of Dinosaurs. St. Martin's Press. ISBN 0312262264.
- Paul, Gregory S. (2002). Dinosaurs of the Air: The Evolution and Loss of flight in Dinosaurs and Birds. Baltimore: The Johns Hopkins University Press. ISBN 0801867630.
- M Schweitzer, JL Wittmeyer and JR Horne (2005). Gender-Specific Reproductive Tissue in Ratites and Tyrannosaurus rex. Science 308; 5727:1456-60.
- Weishampel, David B. (2004). The Dinosauria. University of California Press; 2nd edition. ISBN 0520242092.
- Keith M Parsons. (2001). Drawing Out Leviathan. Indiana University Press. ISBN 0253339375. ;Technical papers
- Belinda S. W. Chang, Karolina Jönsson, Manija A. Kazmi, Michael J. Donoghue and Thomas P. Sakmar. (2002). [http://mbe.oupjournals.org/cgi/content/full/19/9/1483 Recreating a functional ancestral archosaur visual pigment]. Molecular Biology and Evolution 19 (9), 1483–1489.
- Hai-Lin Wang, Zi-Yang Yan and Dong-Yan Jin. (1997). [http://mbe.oupjournals.org/cgi/reprint/14/5/589 Reanalysis of published DNA sequence amplified from Cretaceous dinosaur egg fossil]. Molecular Biology and Evolution 14 (5), 589–591.

External links and sources

;For children
- [http://www.mantyweb.com/dinosaur/ Dinosaur Time Machine from MantyWeb Educational Software] From MantyWeb Educational Software. Kid's site, facts, games.
- [http://yahooligans.yahoo.com/content/science/dinosaurs Dinopedia] From Yahooligans! Science. Glossaries, dino cards and indexes.
- [http://www.enchantedlearning.com/subjects/dinosaurs/ Zoom Dinosaurs] From Enchanted Learning. Kid's site, info pages, theories, history. ;Popular
- [http://www.nhm.ac.uk/nature-online/life/dinosaurs-other-extinct-creatures/index.html Dinosaurs & other extinct creatures] From the Natural History Museum. London popular site, well illustrated dino directory.
- [http://www.arches.uga.edu/~rfreeman/GEOL3350_'4HistoryDinoSt.htm History of Dinosaur discovery] Timeline of the discovery of Dinosaurs.
- [http://pubs.usgs.gov/gip/dinosaurs/ Dinosaurs: Facts and Fiction] From the United States Geological Survey. Popular overview.
- [http://www.bbc.co.uk/dinosaurs/ Dinosaurs] From the BBC. Popular site, very well illustrated.
- [http://www.dinodata.net/Discussions/dinosaurs.html Discussions] From DinoData. Summaries of modern debates about dinosaurs.
- [http://www.ucmp.berkeley.edu/diapsids/dinosaur.html Dinosauria] From UC Berkeley Museum of Paleontology Detailed information - scroll down for menu.
- [http://www.dinosaurnews.org/ The Dinosaur News] The Dino-headlines from around the world. Recent news on dinsaurs, including finds and discoveries, lots of links.
- [http://www.bowdoin.edu/~dbensen/ OPUS: Dinosaur by Daniel Bensen] A gallery of dino-paintings. ;Technical
- [http://www.prehistoricplanet.com/ Prehistoric Planet] From PaleoClones. Current dino news.
- [http://www.wired.com/news/technology/0,1282,63613,00.html A Fiery Death for Dinosaurs? by Amit Asaravala] From Wired. Article on the rapid extinction of dinosaurs.
- [http://www.newscientist.com/hottopics/dinosaurs/ The Rex Files] From the New Scientist. Articles, latest news but out of date.
- [http://palaeo-electronica.org/ Palaeontologia Electronica] From Coquina Press. Online technical journal.
- [http://www.thunderbolts.info/tpod/2005/arch05/050623impossible-dinosaur.htm Impossible Dinosaurs] Article on a gravity-based approach for the extinction by David Talbott and Wallace Thornhill.
- [http://uk.arxiv.org/abs/hep-ph/0002255 TeV scale gravity, mirror universe, and ... dinosaurs] Article from [http://th-www.if.uj.edu.pl/acta/ Acta Physica Polonica B] by Z.K. Silagadze. ;Very technical
- [http://www.dinodata.net DinoData] Technical site, essays, classification, anatomy.
- [http://www.dinosauria.com/dml/dml.htm Dinosauria On-Line] Technical site, essays, pronunciation, dictionary.
- [http://dino.lm.com/ The Dinosauricon] By T. Michael Keesey. Technical site, cladogram, illustrations and animations.
- [http://www.palaeos.com/Vertebrates/Units/Unit310/000.html Dinosauromorpha Cladogram] From [http://www.Palaeos.com Palaeos]. A detailed and wonderful amateur site about all things paleo.
- [http://palaeo.gly.bris.ac.uk/dinobase/dinopage.html Dinobase] AA dinosaur database with dinosaur lists, classification, pictures, and more. ;Bird-dinosaur discussion
- [http://www.ucmp.berkeley.edu/diapsids/avians.html DinoBuzz] Are birds Dinosaurs?
- [http://www.dinosauria.com/ Dinosauria] Site focussing on the Dino-Bird aspect.
- Category:Paleontology Category:Paleozoology Category:Prehistoric reptiles

Gliding

Gliding (or soaring) is a recreational activity and competitive sport where individuals fly un-powered aeroplanes known as gliders or sailplanes. Properly, the term gliding refers to descending flight of a heavier-than-air craft when gravity (its own weight) is its sole motive force; soaring is the correct term to use when the craft gains altitude or speed from movements of the atmosphere during the flight. The words gliding and soaring are also used to describe the ways birds capable of flight remain aloft without flapping their wings; the mechanics of this process are explained in the article on bird flight, while this article focuses on aircraft. bird flight

Recreation vs. sport

While recreational glider enthusiasts enjoy the freedom, scenic views and sheer enjoyment of controlling the planes, others compete (up to World Championship level), or practise competing, by flying as quickly as possible around a circuit defined by "turning-points". These competitions test the pilots' (and, in two-seat gliders, the co-pilots') ability to recognise and make use of local weather conditions, their flying skills and navigational abilities. There are also glider aerobatics competitions. All methods of launching gliders (apart from self-launching motor-gliders) require assistance from other participants and so sailplane pilots band together within clubs to share an airfield and launch equipment, and to maintain high safety standards. Since assistance is also needed to rig and retrieve gliders as well as to train new pilots, there is an important social aspect to the sport.

History

All developments in heavier-than-air flight between 1853 (Sir George Cayley's coachman), and 1903 (Wright brothers) involved gliders (See History of Aviation). However, the sport of gliding only emerged after the First World War and the reason for its development can be traced to the Treaty of Versailles. The peace settlement imposed severe restrictions on the manufacture and use of single-seater powered aeroplanes in Germany. Thus, in the 1920s and 1930s, while aviators and aircraft makers in the rest of the world were working to improve the performance of powered aeroplanes, the Germans were designing, developing and flying ever more efficient gliders and discovering ways of using the natural forces in the atmosphere to make them fly further and faster. The first German gliding competition was held at the Wasserkuppe in 1920, organised by Oskar Ursinus, and ten years later had become an international event. The sport has since been taken up in many countries. It does not matter whether the countries are flat or mountainous, hot or temperate, because gliders can soar in most places. Germany, however, remains the world centre of gliding, as evinced by the fact that all the major glider manufacturers are still based there. Oskar Ursinuss and light winds.]]

Soaring

Soaring is usually achieved by flying through a mass of air that is ascending as fast or faster than the sailplane is descending, and thus gaining potential energy. The most commonly used rising masses of air are thermals (updrafts of warm air), ridge lift (found where the wind blows against the face of a hill and is forced to rise), and wave lift (standing waves in the atmosphere, analogous to the ripples on the surface of a stream). Ridge lift rarely allows pilots to climb much higher than about 2,000 ft (600 m) above the terrain; thermals, depending on the climate and terrain, can exceed 10,000 ft (3,000 m) in flat country and much higher in the mountains; wave lift has allowed gliders to achieve altitudes approaching 50,000 ft (15,000 m). On rare occasions, glider pilots have been able to use a technique called "dynamic soaring", where a sailplane can be made to gain kinetic energy by repeatedly crossing the boundary between air masses of different horizontal velocity. However, such zones of high "wind gradient" are usually much too low to be used safely by aircraft, so dynamic soaring is a technique only really useful to radio control model aircraft and to birds, notably to the albatrosses who during long flights can be seen repeatedly pulling up, turning, and diving back down through the wind gradient close to the surface of the ocean. In thermal flight, the glider pilot attempts to find streams of air that are moving upwards as a result of being heated by contact with sun-lit earth. If the air contains enough moisture, the water will condense from the rising air and form cumulus clouds. Well-formed cumulus clouds (the fluffy, cotton-wool type of cloud) with sharply defined flat bases often form at the tops of strong thermals. Once a thermal is encountered, the pilot banks sharply to keep the plane turning in a small circle within the thermal and so can ride upward. Rates of climb depend on conditions, but several metres per second is common. As it requires rising heated air, thermalling is typically only effective in mid-latitudes from spring through into late summer. Other latitudes often have a layer of warm air, an inversion, which stops the air in the thermals from rising higher. During winter the solar heat can only create weak thermals. In a few countries gliders can continue to climb into the clouds in uncontrolled airspace but in many countries the pilot must stop climbing at cloud-base (see Visual Flight Rules). Sometimes thermals do not create cumulus clouds. This can happen when the air has little moisture or when an inversion stops the thermal from rising high enough for the moisture to condense. Without clouds to mark the thermals, the pilot must use his skill and luck to find them. Typical locations to find thermals are over towns, freshly ploughed fields and asphalt roads, however thermals are often hard to associate with any feature on the ground. A pilot who is ridge soaring looks for air that is being lifted as it flows up the sides of hills. Ridge lift is present whenever the wind blows in any weather but sometimes it is augmented by thermals when the slopes also face the sun. Mountain waves give long stretches of rising air and allow gliders to climb high, long before the sun has started heating the ground. Most sailplane altitude records have therefore been set by using in mountain waves from long mountain ranges all over the world. The current [http://records.fai.org/gliding/#current World Distance Record] of 3008 km by Klaus Ohlmann (on 21 Jan 2003) was also flown in the mountain wave in South America. Long, stationary lenticular (lens-shaped) clouds, perpendicular to the wind direction, frequently mark the crests of atmospheric waves. A rare phenomenon known as Morning Glory has also been used by sailplane pilots in Australia.

Badges

Achievements in gliding have been marked by the awarding of badges since the 1920s. For the lower badges national glider federations set their own criteria. For example, in the United States an "A" badge is issued for the first solo, while "B" and "C" require longer flights and more training. A bronze badge shows preparation for cross-country work, including spot landings and a pair of two hour flights. The higher badges follow the standards set down by the Federation Aeronautique Internationale. Earning the Silver Badge shows that a glider pilot has achieved an altitude gain of at least 1000m, made a five-hour duration flight, and has flown cross-country for a straight-line distance of at least 50km: usually, but not invariably, in separate flights. The [http://www.fai.org/sporting_code/sc3.asp FAI Sporting Code] defines the rules for observers and recording devices to validate the claims for badges. In the United States alone, over 6000 Silver Badges have been issued. The Gold and Diamond Badges require pilots to fly higher and farther. A pilot with the three "Diamonds" has flown 300km to a pre-defined goal, has flown 500km in one flight (but not necessarily to a pre-defined goal) and gained 5000m in height. The FAI also issues diplomas for 1000km and thereafter in increments of 250km. The ultimate challenge is to add a 2000 km diploma for a single flight exceeding that distance. Only a few people have ever achieved it. National federations also issue other badges. For example, The Soaring Society of America also issues badges for going above 25,000 feet (7,620 m) and for enough cross-country flying to circle the world. The British Gliding Association issues a 750km diploma, because only two flights over 1000km have ever been possible in the UK's climate.

Launch methods

British Gliding Association British Gliding Association British Gliding Association British Gliding Association Gliders are initially launched into the air by one of several methods, the most common are "aerotowing" and "winching". Aerotows normally use single engined light aircraft, but lately, powerful self-launching motor gliders and microlight planes have also been permitted to tow gliders. The tow aircraft takes the glider to the desired height and place and the pilot releases the rope. Aerotow ropes are typically made of polypropylene rope and are between 50 and 60 metres in length. At the tow plane end, a weak link is fitted to the rope to ensure that any sudden loads imposed by the glider getting out of station do not damage the airframe of the tow plane. During the aerotow, the glider pilot keeps the glider "in station" behind the tow plane. This can either be the "low tow" position, just below the slipstream of the tow plane propellor, or the "high tow" position just above the slipstream. Over the years there has been great debate about which of these two positions is the safest, and there has been no universal agreement. In Australia the convention is to fly in low tow, whereas in the United States the high tow prevails. One interesting aerotow variation is to perform a "dual tow" in which two gliders are attached to the one tow plane, using ropes of different lengths. This certainly looks spectacular, but requires skill and precise flying by all concerned. Gliders are often launched using a stationary ground-based winch, sometimes mounted on a heavy vehicle. This method is widely used in many European countries, often in addition to aerotowing. The engine is usually from a large car or a diesel truck (sometimes using LPG), though hydraulic fluid engines and electrical motors are sometimes used. The winch pulls in a 1000 to 1600 m long cable made of steel wire or a synthetic fibre which is attached to the glider. The glider releases the cable at a height of about 400 to 500m after a very short and steep ride. A winch launch costs between EUR 3 and EUR 10, which is much less than an aero-tow. One disadvantage of winch launching is that the launch height is variable with the wind strength and cable run length, which could mean that the duration of flights is slightly shorter unless the pilot is fortunate enough to make contact with a thermal or other source of lift within a few minutes of releasing the cable. Gliders can also be launched from the top of a hill into a stiff breeze using a rubber band, or "bungee". For this launch method, the glider's main wheel rests in a small concrete trough. The hook that is normally used for winch-launching is used instead to attach the middle of the bungee. Each end of the bungee is then pulled by 3 or 4 people. One group runs slightly to the left, the other to the right of the glider. Once the tension in the bungee is high enough, the pilot releases the wheel brake and the glider's wheel pops out of the trough. The glider gains just enough energy to leave the ground and fly away from the hill. Another launch method, now rarely used, is the "autotow". This needs a long runway, a large pick-up truck and a length of cable. After gently taking up slack in the cable, the driver accelerates hard and the glider rises like a kite to as much as 400 metres if there is a good headwind and a 1.5 km runway. A variation on this is the "reverse pulley" method in which the car drives towards the glider that it is launching; the cable connecting the car and glider passes around a pulley at the far end of the airfield.

Cross-country

Gliders can stay airborne for hours if the conditions are good. This enables gliders to fly long distances at surprisingly high speeds. Although Klaus Ohlmann's world record is obviously not a typical flight, even in less favourable places in Europe, good pilots usually have flights over 500 kilometres every year at average speeds of 80 km/h or faster. In addition to just trying to fly further, gliders also race each other. As the performance of gliders improved in the 1960s, the concept of flying as far away as possible became unpopular with the crews who had to retrieve the gliders. Pilots now win contests by being the fastest around a pre-defined course back to the starting point, or, if the weather is not as good as expected, the furthest round the course. Originally proof of getting to the turning points was by observing the gliders from the ground. Later the pilots took photographs of the turn-points but nowadays gliders carry secure devices that record the position every few seconds from GPS satellites. National competitions generally last one week but international championships are normally over two weeks. The winner is the pilot who has amassed the greatest number of points over all the contest days. Because it would be unsafe for many gliders to cross a start line at the same time, pilots can choose their own start time. Gliders are not visible to spectators for long periods of each day's contest and scoring is complex, so gliding has been a difficult sport to televise. This means that soaring is a sport in which most contestants are still amateurs. However, a new format contest has been introduced [http://www.cnvv.net/wsgp/en/accueil-en.htm see Sailplane Grand Prix]. Also gaining popularity in recent years is an informal online contest called the [http://www.onlinecontest.org OLC] where pilots upload their GPS data files and are automatically scored based on distance flown. Nearly 9,000 pilots worldwide participate. Soaring pioneer Paul MacCready developed a mathematical theory for optimizing cross country soaring speeds. His theory allows one to compute the optimal cruising speed between thermals, accounting for thermal strength, sailplane performance and other variables. The theory accounts for the fact that if a pilot flies faster between thermals, the next thermal is reached sooner. However the glider also sinks faster, requiring the pilot to spend more time circling to regain the altitude. The MacCready speed represents the optimal tradeoff between cruising and circling. Most competition pilots make use of MacCready theory to optimize their flight speeds, and have the necessary calculations programmed in their flight computers.

Outlandings

Paul MacCready Sometimes a pilot on a cross-country flight finds that the weather is not as good as expected. In these circumstances, the pilot must choose a field and 'land-out'. Landing out is a routine event in cross-country gliding, though they are often mistaken for 'emergency landings'. They are entirely normal, although they are an inconvenience. The pilot has to choose from the air a field that is safe to land in and which does not cause damage to the property. The glider and pilot can be retrieved by pilot's ground crew using a purpose-built trailer which can easily be towed by a car. Alternatively, if the glider has landed in a suitable field, a tow plane can be summoned to re-launch the aircraft (with the permission of the field's owner of course). To avoid the inconvenience of landing out, some gliders have a small engine and a retractable propeller. Some of these engines are not powerful enough to launch the glider, but they can provide enough power to allow gliders to stay airborne and so to return to their home airfields. However, an engine has to be started at a height that includes a margin that would still allow a safe outlanding to be made, if the engine were to fail to start. Consequently gliders without an engine will sometimes be able to thermal safely below that height, find lift and continue on their task. An engine also adds to the weight and expense of a glider.

Hazards

Although considered a relatively safe form of aviation, there are potential hazards in gliding. Gliders, however, surround the pilot with a strong structure and most accidents occur at a low speed causing no injuries. A small number of fatal accidents occur every year, almost all caused by pilot error. Causes include:
- loss of control during take-off and landing: the majority of fatal accidents take place during operations close to the ground and are typically the result of pilot error.
- mid-air collisions: gliders sometimes fly in close proximity, especially in thermals. Glider pilots have to keep a good look-out and many fly with parachutes for this reason.
- in-flight structural failures: these occur rarely, usually the result of high loads placed on the aircraft either intentionally (during aerobatics) or while recovering from a sudden loss of control.
- unconnected controls: gliders are designed for quick assembly. While most newer gliders use automatic control hookups, the majority of sailplanes have manual quick connect control rods. If neglected or improperly engaged prior to flight, a pilot might lose control of the glider.
- outlandings: there is some risk of striking power lines or other unseen objects by cross-country pilots during an outlanding
- contact with terrain: turbulence can result in a sudden loss of control and altitude. The stronger the wind, the more varied the terrain, the greater the risk of severe turbulence. Pilots who fly in mountainous terrain are especially wary of this danger.
- thunderstorms: the thermals pilots use for soaring sometimes blossom into thunderstorms, with severe turbulence, hail, and lightening, each of which presents serious danger to gliders.

Learning to glide

Paul MacCready Most clubs offer trial lessons to people interested in learning to glide and will accept bookings by phone. The links to national organisations below give the contact details for the nearest clubs. The pupil flies with an instructor in a two-seat glider fitted with dual controls. The instructor does the first launches and landings but otherwise the pupil uses the controls. People with the skill to drive a car can usually learn to fly a glider. Some clubs offer courses over several days, though, with a mixture of winch and aerotow launches, it often takes ab initios at least 50 training flights before they are allowed to fly solo. If winches are used, the cost of learning to glide is much less than that of learning to fly powered aircraft. However the cost is much greater if aerotowing is the only available method of launching, even though fewer launches might be needed, perhaps as few as 30. Further training continues after the first solo until the pupil is judged capable of taking a glider cross-country. Some studying is required on topics such as the regulations, use of the radio, weather and navigation.

Famous glider pilots

- Neil Armstrong - astronaut
- John Denver - singer/songwriter
- Steve Fossett - entrepreneur and record breaker
- Barron Hilton - hotel magnate
- Paul MacCready - aviation inventor
- Steve McQueen - actor
- Mike Melvill - Spaceship One test pilot
- Robert Pearson - (also glided a Boeing 767)
- Derek Piggott - movie stunt pilot
- Christopher Reeve - actor
- Hanna Reitsch - test pilot
- Cliff Robertson - actor
- Peter Scott - naturalist (founder of World Wildlife Fund)

Some national gliding associations

- British Gliding Association
- Gliding Federation of Australia
- Gliding New Zealand
- Royal Canadian Air Cadets
- Soaring Society of America
- Soaring Society of South Africa

Related sports

Two minimalistic variations of the sport are hang gliding, where instead of a fully-fledged plane with full control surfaces and an enclosed cockpit the craft used is basically a fabric flying wing, and paragliding, where a sophisticated kind of parachute is flown.

External links

- [http://start.fai.org/gliding-federations.asp Links to all national gliding federations]
- [http://www.fai.org/gliding/ International Gliding Commission]
- [http://www.glidingmagazine.com/ Gliding Magazine]
- [http://www.onlinecontest.org/olcphp/olc-i.php?olc=olc-i International Gliding Online Contest]
- [http://www.aircross.co.uk/sisteron/ Gliding in the French Alps]
- [http://soaring.aerobatics.ws/ Soaring Services]
- [http://www.whiteplanes.com/gliders1.htm Gliding pictures]
- [http://www.alpenstreckenflug.de/texte/english/glidingvideos.htm Videos] category:Aeronautics category:aviation Category:Gliding

Evolution

, based on rRNA gene data, showing the separation of the three domains, bacteria, archaea, and eukaryotes, as described initially by Carl Woese.]] In biology, evolution is the process by which populations of organisms acquire and pass on novel traits from generation to generation, affecting the overall makeup of the population and even leading to the emergence of new species. The terms organic evolution or biological evolution are often used to distinguish this meaning from other usages. The development of the modern theory of evolution began with the introduction of the concept of natural selection in a joint 1858 paper by Charles Darwin and Alfred Russel Wallace. This theory achieved a wider readership in Darwin's 1859 book, The Origin of Species. Darwin and Wallace proposed that evolution occurs because a heritable trait that increases an individual's chance of successfully reproducing will become more common, by inheritance, from one generation to the next, and likewise a heritable trait that decreases an individual's chance of reproducing will become rarer. This work was groundbreaking, and overturned other evolutionary theories, such as that advanced by Jean Baptiste Lamarck. Because of its potential implications for the origins of humankind, the theory has been at the center of many social and religious controversies since its first inception (see Creation-evolution controversy). In the 1930s, scientists combined Darwinian natural selection with the re-discovered theory of Mendelian heredity to create the modern synthesis, now one of the fundamental scientific theories of biology. In the modern synthesis, "evolution" is defined as a change in the frequency of alleles within a population from one generation to the next. The basic mechanisms that produce these changes are natural selection, genetic drift, and genetic variation. The primary sources of genetic variation are mutation, sex, and gene flow.

Overview of evolution

Evidence of evolution

The process of evolution has left behind numerous records which reveal the history of species. While the best-known of these are the fossils, fossils are only a small part of the overall physical record of evolution. Fossils, taken together with the comparative anatomy of present-day plants and animals, constitute the morphological record. By comparing the anatomies of both modern and extinct species, biologists can reconstruct the lineages of those species with some accuracy. Using fossil evidence, for instance, the connection between dinosaurs and birds has been established by way of so-called "transitional" species such as Archaeopteryx. The development of genetics has allowed biologists to study the genetic record of evolution as well. Although we cannot obtain the DNA sequences of most extinct species, the degree of similarity and difference among modern species allows geneticists to reconstruct lineages with greater accuracy. It is from genetic comparisons that claims such as the 98-99% similarity between humans and chimpanzees come from, for instance. Other evidence used to demonstrate evolutionary lineages includes the geographical distribution of species. For instance, monotremes and most marsupials are found only in Australia, showing that their common ancestor with placental mammals lived before the submerging of the ancient land bridge between Australia and Asia. Scientists correlate all of the above evidence – drawn from paleontology, anatomy, genetics, and geography – with other information about the history of the earth. For instance, paleoclimatology attests to periodic ice ages during which the climate was much cooler; and these are found to match up with the spread of species such as the woolly mammoth which are better-equipped to deal with cold.

Morphological evidence

Fossils are important for estimating when various lineages developed. As fossilization on an organism is an uncommon occurrence, usually requiring hard parts (like bone) and death near a site where sediments are being deposited, the fossil record only provides sparse and intermittent information about the evolution of life. Fossil evidence of organisms without hard body parts, such as shell, bone, and teeth, is sparse but exists in the form of ancient microfossils and the fossilization of ancient burrows and a few soft-bodied organisms. Fossil evidence of prehistoric organisms has been found all over the Earth. The age of fossils can often be deduced from the geologic context in which they are found; and their absolute age can be verified with radiometric dating. Some fossils bear a resemblance to organisms alive today, while others are radically different. Fossils have been used to determine at what time a lineage developed, and transitional fossils can be used to demonstrate continuity between two different lineages. Paleontologists investigate evolution largely through analysis of fossils. Phylogeny, the study of the ancestry of species, has revealed that structures with similar internal organization may perform divergent functions. Vertebrate limbs are a common example of such homologous structures. Bat wings, for example, are very similar to hands. A vestigial organ or structure may exist with little or no purpose in one organism, though they have a clear purpose in other species. The human wisdom teeth and appendix are common examples.

Genetic sequence evidence

Comparison of the genetic sequence of organisms reveals that phylogenetically close organisms have a higher degree of sequence similarity than organisms that are phylogenetically distant. For example, neutral human DNA sequences are approximately 1.2% divergent (based on substitutions) from those of their nearest genetic r

Bird flight

Evolution and purpose of bird flight

Basic mechanics of bird flight

The wing

Wing shape and flight

Elliptical wings

High speed wings

High aspect ratio wings

Soaring wings with deep slots

Hovering

Take-off and landing

Adaptations for flight

References

Animal locomotion

Paleontology

Overview

Notable paleontologists

Research

See also

External links

Dinosaur

What is a dinosaur?

Definition

Size

Behavior

Study of dinosaurs

Fields of study

Classification

Evolution

Areas of debate

Warm-blooded?

Feathered dinosaurs and the bird connection

Evidence for Cenozoic dinosaurs

Bringing dinosaurs back to life

Discovery of probable soft tissue from dinosaur fossils

Extinction theories

Asteroid collision

The Oort cloud

Environment changes

History of discovery

In popular culture

Notes

See also

References

External links and sources

Gliding

Recreation vs. sport

History

Soaring

Badges

Launch methods

Cross-country

Outlandings

Hazards

Learning to glide

Famous glider pilots

Some national gliding associations

Related sports

External links

Evolution

Overview of evolution

Evidence of evolution

Morphological evidence

Genetic sequence evidence